Development of a CRISPR/Cas9 system in Entamoeba histolytica: proof of concept

Entamoeba moshkovskii as a potential model organism for Gal/GalNAc lectin intermediate subunit exhibition and functional identification

In humans, Entamoeba histolytica is the main pathogen causing various amoebiases, while E. moshkovskii falls between being a pathogen and non-pathogen. The two species have similar behavior patterns but differ significantly in pathogenicity, with previous studies and clinical data indicating that E. moshkovskii has a low level of pathogenicity. Meaningfully, the biological characteristics of E. moshkovskii make it a potential model organism and a protein display platform for studying the functions of important Entamoeba proteins. Here, an Amoeba-pcDNA3.1 vector capable of overexpressing E. histolytica-sourced Igl-C protein was constructed and successfully transfected into E. moshkovskii. High levels of expression of the Igl-C, EGFP, and NeoR genes were identified in Igl-C-transfected trophozoites using qRT-PCR, and they were subsequently confirmed using immunoblotting. Transfection of Igl-C protein improved the adherence and phagocytosis of E. moshkovskii, demonstrating that E. histolytica Igl mediated amoebic adhesion. Moreover, as a manifestation of protein virulence, the ability of post-transfected trophozoites to induce inflammation in host macrophages was also enhanced. In conclusion, this study utilizing the characteristics of E. moshkovskii confirmed its potential to serve as a model organism. E. moshkovskii could replace E. histolytica as the target of gene editing, allowing more efficient study of amoebic pathogenicity.

CRISPR-Cas9-based method for isolating microgametes of Eimeria tenella

Eimeria tenella infections are known to cause severe caecal damage and death of the infected chicken. Gamogony is an essential stage in E. tenella life cycle and in the establishment of coccidiosis. Prior research had extensively explored isolation and separation of the parasite gametes - microgamete (male) and macrogamete (female). However, there is little information on the efficient, highly purified and distinctly separated male and female gametes. In this study, we generated a genome editing line expressing mCherry fluorescent protein fused with GCS1 protein in E. tenella by using Toxoplasma gondii CRISPR-Cas9 system, flow cytometry and fluorescence microscopy. This allowed precise separation of E. tenella male and female gametes in the transgenic parasite population. The separation of male and female gametes would not only build on our understanding of E. tenella transmission, but it would also facilitate development of gametocidal compounds as drug targets for E. tenella infection.

CRISPR-Cas9: Taming protozoan parasites with bacterial scissor

The invention of CRISPR-Cas9 technology has opened a new era in which genome manipulation has become precise, faster, cheap and more accurate than previous genome editing strategies. Despite the intricacies of the genomes associated with several protozoan parasites, CRISPR-Cas9 has made a substantial contribution to parasitology. The study of functional genomics through CRISPR-Cas9 mediated gene knockout, insertion, deletion and mutation has helped in understanding intrinsic parasite biology. The invention of CRISPR-dCas9 has helped in the programmable control of protozoan gene expression and epigenetic engineering. CRISPR and CRISPR-based alternatives will continue to thrive and may aid in the development of novel anti-protozoan strategies to tame the protozoan parasites in the imminent future.

Gene expression of axenically-isolated clinical Entamoeba histolytica strains and its impact on disease severity of amebiasis

The severity of Entamoeba histolytica infection is determined by host immunology, pathogen virulence, and the intestinal environment. Conventional research for assessing pathogen virulence has been mainly performed using laboratory strains, such as a virulent HM-1: IMSS (HM-1) and an avirulent Rahman, under various artificial environmental conditions because of the difficulties of axenic isolation of the clinical strains. However, it is still unclear whether scientific knowledge based on laboratory strains are universally applicable to the true pathogenesis. Hereby, we performed transcriptomic analysis of clinical strains from patients with different degrees of disease severity, as well as HM-1 under different conditions. Even after several months of axenization, Clinical strains show the distinct profile in gene expression during in vitro passage, moreover, difference between any 2 of these strains was much greater than the changes on the liver challenge. Interestingly, 26 DEGs, which were closely related to the biological functions, were oppositely up- or down regulated between virulent Ax 19 (liver abscess) and avirulent Ax 11 (asymptomatic carrier). Additionally, RNAseq using laboratory strain (HM1) showed more than half of genes were differently expressed between continuously in vitro passaged HM1 (in vitro HM1) and periodically liver passaged HM1 (virulent HM1), which was much greater than the changes on the liver passage of virulent HM1. Also, transcriptomic analysis of a laboratory strain revealed that continuous environmental stress enhances its virulence via a shift in its gene expression profile. Changes in gene expression patterns on liver abscess formation were not consistent between clinical and laboratory strains.

Various genotypes of Entamoeba histolytica are prevalent in the field. Some papers suggest the association between genotypes and disease severity. However, most studies for assessing pathogen virulence were performed using laboratory strains, such as virulent HM1: IMSS (HM1) and avirulent Rahman, because axenic isolation from clinical specimen is technically complex and time consuming. This transcriptomic analysis using clinical strains from the patients with different clinical severity, as well as the laboratory strain HM1 under different conditions showed unique gene expression patterns. Following things were confirmed; 1. Virulent clinical strain maintains its virulence with unique gene expression pattern after axenic isolation, 2. Continuous environmental stress enhances its virulence via the accumulation of altered gene expressions, and 3. Changes in gene expression on the liver abscess formation are not always the same amongst strains. For an accurate understanding the pathogenesis, comprehensive analyses of various clinical strains under different environmental conditions should be promoted.

Growth and Genetic Manipulation of Entamoeba histolytica

Entamoeba histolytica is a parasitic protozoan and the causative agent of amoebiasis in humans. Amoebiasis has a high incidence of disease, resulting in ∼67,900 deaths per year, and it poses a tremendous burden of morbidity and mortality in children. Despite its importance, E. histolytica is an understudied parasite. These protocols describe the in vitro growth, maintenance, cryopreservation, genetic manipulation, and cloning of axenic E. histolytica trophozoites. There has been significant progress in genetic manipulation of this organism over the past decade, and these protocols outline the ways in which these advances can be implemented. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Culturing E. histolytica trophozoites Support Protocol 1: Preparation of TYI-S-33 medium Support Protocol 2: Lot testing of Biosate peptone and adult bovine serum for TYI-S-33 medium Basic Protocol 2: Cryopreservation of E. histolytica trophozoites Support Protocol 3: Preparation of cryoprotectant solutions Basic Protocol 3: Transfection of E. histolytica trophozoites with Attractene reagent Basic Protocol 4: Creating clonal lines using limiting dilution Basic Protocol 5: Knockdown of one to two genes with trigger-induced RNA interference Support Protocol 4: Evaluation of RNA interference knockdown with reverse transcriptase PCR Basic Protocol 6: E. histolytica growth curves.

Establishment of quantitative RNAi-based forward genetics in Entamoeba histolytica and identification of genes required for growth

While Entamoeba histolytica remains a globally important pathogen, it is dramatically understudied. The tractability of E. histolytica has historically been limited, which is largely due to challenging features of its genome. To enable forward genetics, we constructed and validated the first genome-wide E. histolytica RNAi knockdown mutant library. This library allows for Illumina deep sequencing analysis for quantitative identification of mutants that are enriched or depleted after selection. We developed a novel analysis pipeline to precisely define and quantify gene fragments. We used the library to perform the first RNAi screen in E. histolytica and identified slow growth (SG) mutants. Among genes targeted in SG mutants, many had annotated functions consistent with roles in cellular growth or metabolic pathways. Some targeted genes were annotated as hypothetical or lacked annotated domains, supporting the power of forward genetics in uncovering functional information that cannot be gleaned from databases. While the localization of neither of the proteins targeted in SG1 nor SG2 mutants could be predicted by sequence analysis, we showed experimentally that SG1 localized to the cytoplasm and cell surface, while SG2 localized to the cytoplasm. Overexpression of SG1 led to increased growth, while expression of a truncation mutant did not lead to increased growth, and thus aided in defining functional domains in this protein. Finally, in addition to establishing forward genetics, we uncovered new details of the unusual E. histolytica RNAi pathway. These studies dramatically improve the tractability of E. histolytica and open up the possibility of applying genetics to improve understanding of this important pathogen.

Entamoeba histolytica-Gut Microbiota Interaction: More Than Meets the Eye

Amebiasis is a disease caused by the unicellular parasite Entamoeba histolytica. In most cases, the infection is asymptomatic but when symptomatic, the infection can cause dysentery and invasive extraintestinal complications. In the gut, E. histolytica feeds on bacteria. Increasing evidences support the role of the gut microbiota in the development of the disease. In this review we will discuss the consequences of E. histolytica infection on the gut microbiota. We will also discuss new evidences about the role of gut microbiota in regulating the resistance of the parasite to oxidative stress and its virulence.